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Thread: Flex a lite fan high and low?

  1. #1

    Lightbulb Flex a lite fan high and low?

    Hey guys just installed my electric fan harness to factory pin out 42 and Ac clutch for one fan.
    Typical install but im confused after searching the forum and diff post but not exactly anything helpful.

    Im confused on the low high setting etc.
    Fan 1 and Fan 2
    Is Fan 1 just that fan or would that be my low and Fan 2 my high?

    Trying to get ready for 100 plus degree weather in the summer with an all aluminum radiator. Sitting in traffic the temps rise very quickly so both fans on high is a must!

  2. #2
    Ok had some time to look at my settings again. In the editor I have the Fan 1 first speed set 175 on 170 off. Fan 2 looks to be the second fan speed I have at 185 on 180 off. Keep in mind im just trying to get everything to work and from what I can tell the low speed on the fans are even worth having its way too slowwwww. But high setting is a must! I open the vcm scanner and can toggle off and on for the fan 1 low speed and it works fan minus going to slow to cool anything. On fan 2 I have nothing no on or off. What am I missing here?

    Guess it helps to state my truck is a 00 Silverado

  3. #3
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    Post your file. Likely you don't have the second fan enabled in your calibration.
    Last edited by gofastwclass; 04-07-2015 at 03:48 PM.

  4. #4
    Silverado 2000.hpt

    Ok after today got home and check it. Ive been running my Ac to keep the one fan on high while I drive. Surprisingly both fans where on high. But if I turn the Ac off it turns both fans back to low.

    Also under the engine tab then Idle then Air Flow there is the Cooling Fan Air to compensate the idle for when stopped and the fans put a load on the Alternator. How do I know how to adjust this for my vehicle? both fans together on high pull around just shy of 40 amps total.

    Also when I use the scanner to turn on the fans high off and on, I hear something behind the dash. one of the flapper door for the AC?

    thanks for the help gofast!
    Attached Files Attached Files

  5. #5
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    To fix the high / low thing, I would honestly skip the low speed and simply run high speed only - but that is my preference with non OEM fans. Some fans are useful at low speed, most non OEM fans won't move enough air. This is something you will have to judge after reviewing the cooling results in your application. My cars will all cool down from 220 to the thermostat temperature with a single OEM style fan sitting in a parking lot on a hot day with the AC on using a single speed fan.

    I'm not sure what thermostat you are running, but with the fan 1 on temp set at 170° and fan 2 set for 180°, the fans will run almost constantly once the engine gets up to temp on all but the coolest days. Even with a 160° degree thermostat, the engine will flash above that temperature before the thermostat opens. I wouldn't have the fan come on any less than 15 degrees higher than the thermostat temperature or the fans will either stay on (bad) or flutter off and on as the temperature cycles (also bad).

    To get the second fan control working go to "System, A/C" the top field says "Recirc Option" and has a drop down. Yours is set for "AC Recirc" and to run dual fans it needs to be "fan #2" which also requires a wiring change. Since you are in a stock Silverado, you may want to see if this has an adverse effect on your AC recirculation option since I've never done this in a stock vehicle (I usually do swaps). The sound you were hearing when you did your testing what was the recirculation door closing and opening when you choose fan 2.

    I simply leave the cooling fan airflow as is or adjust it in small amounts only if the engine is trying to idle erratically or stall while the fans come on.

  6. #6
    I changed the fan 2 option like you said yesterday doesn't do anything. Still the flapper door sound. what do you mean wiring change? I think your right on the high low and just using high. Once 100+ weather hits they will both be running on high constantly. How would I achieve this?

    I don't really see the usefulness of this harness vs my other relay set up. Im trying to get away from the switches.
    Last edited by SuperSportSteve; 04-08-2015 at 07:16 PM.

  7. #7
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    If you are going to only use the high speed side of the fans, just wire that to the fan 1 output relay to the high speed input for the fans. I would also adjust the coolant temps as I previously mentioned or the fans will run all the time. Letting the PCM control the fans allows the PCM to run them with the AC as well. This has worked well for me in the past and gives you ice cold AC even while the vehicle idles for some time.

    The fan 2 output is the same physical wire as the AC recirculation motor is tied to, but the programming changes it's function within the PCM. There are several multi-function outputs across these PCM's based on programming. The reason you hear the door move when you activate fan 2 in the scanner is the trigger is the same, but the programming tells the PCM if the output is attached to a fan (temperature sensitive) or AC (condition sensitive). In your case (stock truck) I would skip the fan 2 option and stay with a single output (or change the wiring and lose the AC recirculation function). Apparently you live somewhere like me where temps reach 100° at various points so doing this and losing ice cold AC is not a realistic option.

    When done properly, no switches or input from you is required since the PCM handles everything.

  8. #8
    Ill keep you updated Go Fast, it hasnt been that hot here in texas lately!